If your going to buy a Macaw, I would go with a handfed baby. They tend to bond to one person and getting an adult might give you some problems. It kinda depends on the individual bird, but your usually better off with a handfed baby.
I don't know if you live somewhere where noise might be a problem, but keep in mind these birds can be *very* loud. If you have never been in a small room with one when they decide to let the world know they are there.... you ought to try it
They also require a lot of attention, don't think you can get one and just look at it and get it out to play a few times a week, you will end up with a problem bird. Nolagurl is right about the lifespan also, if you provide proper care expect to leave the bird to someone in your will. Have you had experience with large parrots before? If not maybe you should think about a smaller parrot, there are many smaller conures and such that have the same intelligent personalities that are easier for a first time bird owner. I'm not trying to discourage you, just want you to know the downside. Too many of these birds are purchased by people who find out later that they just can't handle them and they are passed off on someone else and because of the bonding thing... this is very hard on the birds.